Hydrocracking of hydrocarbon feedstocks is often used to convert lower value hydrocarbon fractions into higher value products, such as conversion of vacuum gas oil (VGO) feedstocks to diesel fuel and lubricants. Typical hydrocracking reaction schemes can include an initial hydrotreatment step, a hydrocracking step, and a post hydrotreatment step. After these steps, the effluent can be fractionated to separate out a desired diesel fuel and/or lubricant oil basestock.
One method of classifying lubricating oil basestocks is that used by the American Petroleum Institute (API). API Group II basestocks have a saturates content of 90 wt % or greater, a sulfur content of not more than 0.03 wt % and a VI greater than 80 but less than 120. API Group III basestocks are the same as Group II basestocks except that the VI is at least 120. A process scheme such as the one detailed above is typically suitable for production of Group II and Group III basestocks from an appropriate feed.
U.S. Pat. No. 6,884,339 describes a method for processing a feed to produce a lubricant base oil and optionally distillate products. A feed is hydrotreated and then hydrocracked without intermediate separation. An example of the catalyst for hydrocracking can be a supported Y or beta zeolite. The catalyst also includes a hydro-dehydrogenating metal, such as a combination of Ni and Mo. The hydrotreated, hydrocracked effluent is then atmospherically distilled. The portion boiling above 340° C. is catalytically dewaxed in the presence of a bound molecular sieve that includes a hydro-dehydrogenating element. The molecular sieve can be ZSM-48, EU-2, EU-11, or ZBM-30. The hydro-dehydrogenating element can be a noble Group VIII metal, such as Pt or Pd.
U.S. Pat. No. 7,371,315 describes a method for producing a lubricant base oil and optionally distillate products. A feed is provided with a sulfur content of less than 1000 wppm. Optionally, the feed can be a hydrotreated feed. Optionally, the feed can be a hydrocracked feed, such as a feed hydrocracked in the presence of a zeolite Y-containing catalyst. The feed is converted on a noble metal on an acidic support. This entire converted feed can be dewaxed in the presence of a dewaxing catalyst.
U.S. Pat. No. 7,300,900 describes a catalyst and a method for using the catalyst to perform conversion on a hydrocarbon feed. The catalyst includes both a Y zeolite and a zeolite selected from ZBM-30, ZSM-48, EU-2, and EU-11. Examples are provided of a two stage process, with a first stage hydrotreatment of a feed to reduce the sulfur content of the feed to 15 wppm, followed by hydroprocessing using the catalyst containing the two zeolites. An option is also described where it appears that the effluent from a hydrotreatment stage is cascaded without separation to the dual-zeolite catalyst, but no example is provided of the sulfur level of the initial feed for such a process.